Plug-reversing capacitor-start induction-run motor



Patented Apr. 7,1942

PLUG-REVERSING CAPACITOR-START INDUCTION-RUN MOTOR Lloyd W. Buchanan,Lima, Ohio, assignor to Westinghouse Electric & Manui'acturing Company,East Pittsburgh, Pennsylvania 2a., a corporation of Application January5, 1940, Serial No. 812,525

8 Claims.

My invention relates to single-phase self -starting induction-motors foruse on applications such as cranes, hoists, door-openers, lathes, and onnumerous other applications requiring plugreversing motors, or motorswhich may be very quickly reversed by reversing the starting-windingconnections relative to the main-winding connections. My inventionparticularly relates to capacitor-type motors which are provided with astart-run switch for disconnecting the ca- 10 pacitor-typestarting-winding when the motor reaches a predetermined percentage ofits normal running-speed.

The principal object of my invention is to provide novel and improvedmeans for effecting the 5 plugging reversal of capacitor-motors of thabove-described type. I

More specifically, my invention relates to a plug-reversingcontrol-means utilizing a linevoltage-responsive auxiliary relay whichcan be simply designed in accordance with the linevoltage, withoutrequiring a separate, specially designed relay for each current-ratingof a series of motors of a similar type.

With the foregoing'and other objects in view, my invention consists inthe systems, methods, combinations, circuits and apparatus hereinafterdescribed and claimed and illustrated in the accompanying drawingwherein the single figure is k a diagrammatic view of circuits andapparatus embodying my invention in a preferred form of embodiment.

As shown in the drawing, my invention is utilized in connection with aself-starting singlephase capacitor-type induction-motor having a .35primary member which is wound with a mainwinding 4 and a substantiallyquadrature-related starting-winding 5. The starting-winding i isconnected in series-circuit relation to 8. capacitor 8 which causes thecurrent in the start in: winding-means H to be out of phase with thecurrent in the main-winding 4 when both windings are energized inparallel across the same single-phase line III-L2. The motor is alsoprovided with a secondary member which is shown as the rotor-member I,provided with squirrel-cage windings I, or other equivalent poly-axiallyshort-circuited secondary windingmeans. The rotor member I is mounted ona shaft II which is illustrated as carrying a speedresponsive device orcentrifugal governor II which actuates a start-run switch I2 having twoback-contacts i3 and II.

To reverse the motor, a double-pole doublethrow reversing-switch II isprovided, having input-terminals I6 and output-terminals I1, which 'maybe connected together, in either order of connection or which may bedisconnected from each other, by means of double-throw switchblades I8.

In accordance with my invention, I also provide aline-voltage-responsive relay 20 having an actuating coil 2I,back-contacts 22, and front or make-contacts 23. "I also provide anauxiliary resistor 24 or other auxiliary impedance-device.

The motor-terminals 25 and 26 are connected to the supply-line LIL2through a line-switch 21. The motor-tenninals 25 and 26 .are connectedto the terminals of the main-winding l and also to the input-terminalsI6 of the reversing-switch I5. The output-terminals I! of the reversingswitch are utilized to energize the starting-winding 5 through thecapacitor 6, the centrifugal switch I2 and the back-contact I4 of thecentrifugal switching, device, when the latter.

is in its starting position, as illustrated. The operating coil 2| ofthe relay 20 is initially energizedfwith the line-voltage, from theoutputterminals I'l of the reversing-switch I5, through a circuit whichincludes a conductor 30, and the back-contacts I3 and I4 which areshunted by the centrifugal switch-arm I2 in the starting position of thelatter. When the relay 20 once picks up, a holding-circuit isestablished through the make-contacts 23 of the relay, which connectsthe operating coil 2! across the output-terminals ll of thereversing-switch I5, so that the relay remains-energized as long as itreceives at least a certain critical voltage, which may be of the orderof 50% of the supply-voltage of the line III-L2. A second energizingcircuit for the starting winding-means 5-6 is provided by the relayback-contacts 22 which by-pass the centrifugal switch-circuit I2-I4, sothat-the relay' 20 will cause the starting-winding-means 5-6 to beenergized, across the output-terminals I! of the reversing-switch I5,and hence across the motor-terminals 25 and 26, wheneverthe relay 20 isin its deenergized or non-actuated position, regardless of the positionof the centrifugallyactuated start-run switch I2.

The motor-controller means thus far specifically described, except forthe auxiliary resistor 24, constitute the subject matter of a copendingapplication of W. C. Spear, Serial No. 313,244,

filed January 10, 1940, and assigned to the Westinghouse Electric 8:Manufacturing Company, relating to Self-starting single-phaseinductionmotors with plugging reversing connections.

In accordance with my present invention, the

relay-operating winding 2| is also connected in series with theauxiliary resistor 24, and preferably across the terminals of thecapacitor-winding 5, or, in general, across one of the two parts 5 and 5or the capacitor winding-man or cult 5-5. The purpose of this connectionis to cause the relay-coil 2| to receive sufilcient energization fromthe capacitor-winding 5, even with the resistor 24 connected inseries'with the relay-coil 2|, to pick up this relay when thelinevolta'ge is restored after a momentary flicker or failure of theline-voltage, while the motor is operating, the line-voltage beingquickly restored before the motor has had time to slow down sutficientlyto move the start-run switch from its running position to its startingposition. This re-picking-up operation of the relay 2!! is made polsibleby reason oi. the generated voltage which is induced in the'auxiliary orstarting winding 5 when the motor is in operation, or more definitethestarting-winding 5 and the capacitor 5 is disturbed by the strongstarting-current'in-rush, or reversing-current in-rush, during theseconditions, so that insuiiicient voltage appears across thestarting-winding 5 to cause an actuation of 'the relay 20.

The motor is now rapidly decelerating, under the influence of thereversing torque, and when its speed falls ofi a sufiicient lyby thepartial condition or resonance which is i created by the reapplicationor the line-voltage other, across the line Iii-L2, in the mannerpreviously described.- The motor then rapidly starts, and at a certainpredetermined speed, in

amount, the centrifugal start-run switch I! will return to its startingposition, establishing a second energizing circuit, at the back-contactI 4, for the starting winding-means 5--6. At the same time, thestart-run switch l2 closes its back-contact II, which energizes therelay-coil 2| across the line, and produces an actuation or picking-upof the relay, It will be noted, however, that the relay 20 has remainedin its nonactuated position long enough to cause the motor to decelerateto the speed at which the centriI- ugal switch 12 returns to itsstarting position, at which time the centrifugal-switch contact l4continues to energize the starting winding-means 5-4, even after therelay 20 has opened its backcontacts 22. The motor thereupon continuesto decelerate to standstill, and immediately begins to accelerate againin the reverse direction, with both of the primary windings 4 and 5energized, until, at a predetermined critical speed in the reversedirection, the centrifugal switch lI-I2 again operates and deenergizesthe startingits starting cycle, the centrifugally-actuated start-runswitch l2 suddenly snaps open, breaking the back contacts l3 and I4. Theopening oi the back contact I4 disconnects the starting winding-means.56from the line, so that the motor thereafter operates only on its main orrunning winding 4. The opening of the backcontact l3 breaks the initialenergizing-circuit through the relay-coil 2|, but the relay hasmeanwhile picked up and established its own holding-circuit at itsfront-contacts 23, so that the relay 20 remains in its actuated positionduring the entire normal running-operation of the motor.-

When it is desired to reverse the motor, all that is required is toreverse the double-throw reversing-switch IS. The initial movement ofthe reversing-switch blades I8 deenergizes the output-terminals I! ofthe reversing-switch, thus deenergizing the relay 20, so that the latterdrops out, and returns to its deenergized position, closing itsback-contacts 22. When the reversing-switch blades I8 are moved all theway over to the closed position in the reversed order of energization ofthe output terminals ll of the reversing-switch l5, a circuit will. beimmediately established, through the relay back-contacts 22, to thestarting winding-means 5--6, even though the centrifugal switch I2 is inits running-position with the switch-blade I2 out oi contact with itsback-contact l4. This energization of the starting-winding-means 5-8causes said winding-means to be energized from the line LI-L2 in apolarity which is reversed with respect to its initialstarting-polarity, so that the motor is now energized in such, manner asto dewinding 5, leaving the auxiliary relay 20 energized through itsholding-contact 23, as previously described.

It will be noted that my provision of the relay-exciting-connectionincluding the auxiliary resistor 2 is useful in providing an auxiliarysource of energization for the relay-coil 2|, so as to prevent the relay20 from remaining deenergized after a momentary power-interruption, aslong as the motor-rotor 1 has any considerable speed. This isparticularly true if the powersupply-interruption' to the relay-coil His caused by an opening of the reversing-switch 15, so that the mainmotor-winding 4 remains energized, in which case the motor-speed candrop to a considerably lower value than if both primary windings 4 and 5are deenergized, while the motor is running, before the voltage which isgenerated in the auxiliary winding 5 falls to a value 10W enough topermit the relay 20 to drop out. In practice, it is practicable todesign the relay 20 so that it will drop out when the starting-windingcircuit is deenergized while the motor is running, but the auxiliaryrelay-energizing circuit 24 will cause the relay to pick up again iflinevoltage is again applied to the partially resonant starting-windingcircuit 5-6 while the motor still has any considerable speed.

In this manner, I -make it possible for the motor to withstand amomentary interruption in power, or a momentary opening of the contactsof the reversing-switch l8, quickly thereafter restoring the contacts totheir original position, without causing the relay 20 to permanentlyremain out. This provision of the auxiliary relayenergizing circuit 24is desirable, because otherwise, if the re ay 2'! should drop out andlock itself out while the start-run switch I2 is in its runningposition, the relay 20 would continuously energize the starting winding5. Ordinarily. this starting winding 5 is not designed to becontinuously energized, so that it would be very undesirable for thiscontinuous energizetion to occur.

The fact that I utilize a capacitor 6 in series with the startingwinding is very helpful in making possible the correct operation of therelay-holding circuit including the auxiliary resistor 24, because,"when the motor is running at full speed, the capacitor 6 causes thevoltage appearing across the terminals of the auxiliary winding 5 to besomething like 160% of the linevoltage, so that, ordinarily, alow-current, highresistance impedance-device 24 may be connected inseries with the relay-coil 2|, and still permit the relay-coil toreceive the voltage necessary to cause the relay to pick up and move toits actuated position. Even though the motor is not running at quite itsfull speed at the moment .when the line-voltage is restored, after abrief power-interruption, the auxiliary-winding voltage may obviously beconsiderably less than 160% of the line-voltage, and still affordadequate voltage to pick up' the relay 20, even with impedance 24 inseries with its coil 2|, in the event of a brief opening of either themain line-switch 2'I or of the reversing-switch l8.

When the reversing-switch I8 is reversed, however, and the ine-voltageis applied to the motor with the reversed connection of thestartingwinding, the heavy current-inrush destroys the condition ofpartial resonance between the inductive rcactance of thestarting-winding 5 and the capacitive reactance of the capacitor 6, sothat the starting-winding voltage, under these particular conditions, isnot sufiicient to pick up the relay 20.

When the startingswitch H is in its starting position, the resistor 24is connected in parallel to the starting-capacitor 6, through-theswitchcontacts l2-l3, but because of its high resistance, the resistor24 does not interfere with the relatively low-impedance capacitor 6during the starting-operating.

While I have illustrated my invention in but a single form ofembodiment, which is at present preferred by me. I desire suchillustration to be taken merely as an illustration, and not as exeludingsuch additions, omissions and substitutions as would ordinarily occur tothe skilled workers of the art. I desire, therefore, thatthe appendedclaims shall be accorded the broadest construction consistent with theirlanguage and the prior art. a

I claim as my invention: I

1. In combinatioma self-starting single-phase induction-motor havingrelatively rotating pri-.

'energization of said relay from the line-voltage as long as at least apredetermined voltage is applied thereto, an additional impedance-means,

circuit-means for permanently connecting said relay in seriesv with saidimpedance-means and mary and secondary members, the primary mcm- I herhaving a main-winding'and a substantially quadrature-relatedstarting-winding, a capacitor connected in series-circuit relation tothe starting-winding for producing current out of phase withthe currentin the main-winding, means for establishing starting connections wherebyboth the main-winding and the starting-winding are energized in parallelfrom a single singlephase supply-line, start-run switching-means,operable after the motor has started, for changing the connections ofthe starting-winding and for also changing an auxiliary relayingcircuit, reversing-means for reversing the connections of one of saidprimary-member windings relatively to the other primary-member winding,0. linevoltage-responsive relay' operable, in its nonactuated position,to substantially establish the starting connections of thestarting-winding even across the terminals of one of the two parts ofthe circuit comprising the starting-winding and the capacitor. and meansfor causing said relay to return to its non-actuated position when saidreversing-means is operated.

2. In combination, a self-starting single-phase induction-motor havingrelatively rotating primary and secondary members, the primary memherhaving a main-winding and a substantially quadrature-relatedstarting-winding, a capacitor connected in series-circuit relation tothe starting-winding for producing current out of phase with the currentin the main-winding, means ior establishing starting connections wherebyboth the main-winding and the starting-winding are energized in parallelfrom a single single-phase supply-line, start-run switching-means,operable after the motor has started, for changing the connections ofthe starting-winding and for also changing an auxiliary relayingcircuit,'reversingmeans for reversing the connections of one of saidprimary-member windings relatively to the other primary-member winding,aline-voltageresponsive relay operable, in its non-actuated position, tosubstantially establish the starting connections of the starting-windingeven when the start-run switching-means is in its running condition,means for initially energizing said relay through the auxiliary relayingcircuit of said start-run switching-means when the latter is in itsstarting condition, separate circuit-means for subsequently maintainingthe energization of said relay from the line-voltage as long as at leasta said relayto return to its non-actuated position when saidreversing-means isoperated.

I 3. In combination, a self-starting single-phase induction-motor havingrelatively rotating primary and secondary members, the primary memberhaving a main-winding and a substantially quadrature-relatedstarting-winding, a capacitor connected in series-circuit relation tothe starting-winding for producing current out of phase with the currentin the main-winding, means for establishing starting connections wherebyboth the main-winding and the starting-winding are energized inparallelfrom a single single-phase supply-line, start-runswitching-means, operableaiter the motor has started, for changing theconnections of the starting-winding and for also changing an auxiliaryrelaying circuit, a three-position reversing-switch havinginputterminals, output-terminals and operating means having a firstposition in which the output-termie nals are connected to theinput-terminals in a first order of connection, a second position inwhich theelectrical connection between the input and output terminals isbroken, and a third oi connection, the input-terminals of the re:versing-switch being energized from the single phase supply-line, thestarting-winding being energized from the output-terminals oi thereversing-switch, a line-voltage-responsive relay operable, in itsnon-actuated position, to substantially establish the startingconnections of the starting-winding even when the start-runswitching-means is in its running condition, means for initiallyenergizing said relay from the output-terminals of the reversing-switchthrough the auxiliary relaying circuit or said start-run switching-meanswhen the latter is in its starting condition, separate circuit-means forsubsequent- 1y maintaining the energization 01 said relay from theoutput-terminals of the reversing-switch as long as at least apredetermined voltage is applied thereto. an additional impedance-means,and circuit-means for permanently connecting said relay in series withsaid impedance-means and across the terminals of one oi the two parts ofthe circuit comprising the starting-winding and the capacitor, saidrelay returning to its non-actuated position whenever saidreversingswitch is actuated from its first position to its thirdposition, or vice versa.

4. In combination, a self-starting single-phase induction-motor havingrelatively rotating primary and secondary members, the primary mem herhaving a main-winding and a substantially quadrature-relatedstarting-winding, a capacitor connected in series-circuit relation tothe starting-winding for producing current out of phase with the currentin the main-winding,

and a third position in which the output-terminals are connected to theinput-terminals in a reversed order of connection, the input-terminalsof the reversing-switch being energized from the single-phasesupply-line, the starting-winding being energized from theoutput-terminals oi the reversing-switch, a line-voltage-responsiverelay operable, in its non-actuated position, to substantially establishthe starting connections of the starting-winding even when the start-runswitching-means is in its running condition, means for initiallyenergizing said relay from the output-terminals oi the reversing switchthrough the auxiliary relaying circuit of said start-run switching-meanswhen the latter is in its starting condition, separate circuit-means forsubsequently maintaining the energization of said relay from theoutput-terminals of the reversingswitch as long as at least apredetermined voltage is applied thereto, an additional impedancemeans,and circuit-means for permanently connecting said relay in series withsaid impedancemeans across the terminals of the startingwinding, saidrelay returning to its non-actuated position whenever saidreversing-switch is actuated from its first position to its thirdposition, or vice versa.

5. The invention as defined in claim 1, characterized by said start-runmeans having an actuating means which is automatically responsive to apredetermined function oi the speed 01' the motor.

6. The invention as defined in claim 2, characterized by said start-runmeans having an actuating means which is automatically responsive to apredetermined function of the speed of the motor.

'7. The invention as defined in claim 3, characterized by said start-runmeans having an artuating meals which is automatically responsive to apredetermined function of the speed of the motor.

8. The invention as defined in claim 4, characterized by said start-runmeans having an actuating means which is automatically responsive to apredetermined function ofthe speed of the motor.

LLOYD W. BUCHANAN.

